1. Field of the Invention
The present invention relates generally to optical disk drives of the separate type in which a head for focusing a laser beam onto a recording disk is transferred relative to a fixed optical unit constituting an optical processing means including a light source for emitting the laser beam. More particularly, it is concerned with improvements in a dust-proofing structure between confronting surfaces of the fixed optical unit and the head of the separate type optical disk drive.
2. Description of the Prior Art
Optical disk drives are a data processing means which is capable of recording/reproducing the bulk of information and, therefore, they are widely used in various fields of application such as computers, office automation equipment and domestic composite apparatus as a recording/reproducing means.
The optical disk drives are so constructed as to record and read information on a disk-type recording medium such as an optical disk by using a laser beam. Since a unit piece of information to be recorded or reproduced by the laser beam correspond to a very tiny spot on the optical disk, a path of travel of the laser beam must always be kept clean.
With a wide diversity in application surroundings in view, a keen demand has been voiced for an optical disk drive which is highly resistant to dust and dirt.
A conventional optical disk drive includes, as shown in FIG. 4, a recording disk 1 on which data signals are recorded, a drive motor 2 for rotating the recording disk 1, a fixed optical unit 3 including a light source (not shown) for emitting a laser beam, a head 4 for focusing the laser beam onto a recording surface of the recording disk 1 and for being transferred back-and-forth in the direction indicated by the arrowheads Y1 and Y2, a pair of parallel spaced guide shafts 5 and 5 along which the head 4 is guided in the direction of the arrowheads Y1 and Y2, a pair of coils 6 and 6 mounted on opposite sides of the head 4, and a pair of parallel spaced elongate magnets 7 and 7 extending through the coils 6, 6, respectively, for generating a driving force to transfer the head 4. The laser beam emitted from the fixed optical unit 3 toward the head 4 advances along an optical path 8 indicated by the dashed line. The fixed optical unit 3 has a circular hole 9 defining one end of the optical path 8, while the head 4 has a circular hole 10 aligned with the hole 9 and defining the opposite end of the optical path 8. A cushioning member 12 made of rubber, for example, is disposed between two confronting surfaces of the fixed optical unit 3 and the head 4 to prevent the head 4 from impinging upon the fixed optical unit 3.
The conventional optical disk drive of the foregoing construction operates as follows.
By controlling the magnitude of an electric current supplied to the coils 6, the coils 6 produce a driving force needed for transferring the head 4. The head 4 is displaced back-and-forth along the shafts 5 in the direction indicated by the arrowheads Y1 and Y2. During the reciprocating movement of the head 4 in the direction of the arrowheads Y1 and Y2, the optical path 8 is always maintained without interruption, so that the laser beam is continuously supplied through the aligned holes 9 and 10 to the head 4. Thus, the head 4 is transferred over the recording surface of the recording disk 1 radially between the outer edge and the inner edge of the recording disk 1, thereby performing recording and reproducing operations.
Since the holes 9, 10 on the optical path 8 are exposed to the exterior, dust can easily get in the holes 9, 10. Particularly when the recording disk 1 contained in a protective cartridge (not shown) is loaded in the optical disk drive, it occurs likely that the cartridge is inserted with foreign matter or dust adhering on it. In this instance, when the cartridge is subjected to an impact force at the time of driving the recording disk 1, dust is likely to separate from the cartridge and then adhere to the circumferential walls of the holes 9, 10. The dust is accumulated on the circumferential walls of the holes 9, 10 as the loading and unloading operations are repeated. Due to the presence of foreign matter or dust on the path 8 of travel of the laser beam, the performance characteristics of the optical disk drive are significantly deteriorated.